Release 1.5.3

[friegger]

@dspinhirne Would it be possible to release 1.5.3 to RubyGems? As far as we understand it, it fixes https://nvd.nist.gov/vuln/detail/CVE-2019-17383.

[stuarthannig]

+1, the vulnerability fix needs to be released to Rubygems

[dspinhirne]

i believe this should be fixed, as i updated this in github a while back. pushed to rubygems.